The advance of mobile cellular networks and the popularity of mobile devices combined with the constant growth in user throughput have created a huge demand for at least one resource: spectrum.
There are three main approaches toward spectrum management, which are listed as follows:                License the spectrum to operators that will pay significant fees for the privilege of using dedicated spectrum;        Use unlicensed spectrum where devices are sharing the same spectrum using a set of predetermined rules aimed at insuring fair spectrum access; and        Use shared spectrum, e.g., Licensed Shared Access (LSA) or Authorized shared access (ASA), which usually proposes a division of rights of use, based on time of use or geographical constraints between mobile operators and possibly an incumbent user.        
Embodiments of the present disclosure are concerned with at least the third (last) approach, which proposes a shared spectrum approach. A typical use of the third scenario is to enable use of a band that is available for licensed users in some markets, but is being restricted in others because of incumbents, such as radar or satellite systems. Incumbent systems can be protected around the area of deployment, while authorization for mobile infrastructure can be granted in such a way that aggregate interference from mobile systems towards the incumbent is limited to an acceptable level of noise rise or performance degradation. In LSA, the mobile operator is licensed to operate in permitted or authorized areas, and is the reasonable regulatory approach to ASA.
The introduction of Licensed Shared Access (LSA) in the 2.3 GHz band will allow binary sharing between the incumbent, namely terrestrial radar stations in, for example, France, and Long-Term Evolution (LTE) with the aid of a spectrum repository known as the LSA repository. Such regulation aims at unlocking spectrum designated as an International Mobile Telecommunications (IMT) band in the International Telecommunications Union (ITU) in markets, and subsequently offered a band designation in 3GPP, namely Band 40.
The creation in the United States of America (USA) of the new Citizens Broadband Radio Service (CBRS) in the 3.5 GHz band, currently occupied by incumbents like the Department of Defense, for example, will add much-needed capacity to meet the ever-increasing demands of wireless innovation. The CBRS represents a more aggressive application of ASA to spectrum, where in addition to long-term geographic licenses shared with incumbents, multiple operators may also coexist in close geographical proximity to one another.
Sharing in the 3.5 GHz band occurs between three tiers of users, with higher tiers being accorded lower priority. Access to the spectrum is governed by a Spectrum Access System (SAS) that implements a geolocation database and policy management function to be used to protect incumbents as well as implement a tiered access framework. Incumbent users represent the highest tier in this framework and receive interference protection from Citizens Broadband Radio Service users. Protected incumbents include the federal operations described above, as well as, Fixed Satellite Service (FSS) and, for a finite period, grandfathered terrestrial wireless operations in the 3650-3700 MHz portion of the band. The Citizens Broadband Radio Service itself includes two tiers—Priority Access (PA) and General Authorized Access (GAA)—both authorized in any given location and frequency by an SAS. As the name suggests, Priority Access operations receive protection from GAA operations. Priority Access Licenses (PALs), defined as an authorization to use a 10 megahertz channel in a single census tract for three years, will be assigned in up to 70 megahertz of the 3550-3650 MHz portion of the band. GAA use will be allowed, by rule, throughout the 150 megahertz band. GAA users will receive no interference protection from other Citizens Broadband Radio Service users. The band has been designed for deployment of small cells, although there is sufficient capability in the rules to provision wide area macro deployments, as well.
FIG. 1 illustrates the spectrum anatomy for the 3.5 GHz Citizens Broadband Radio Service. A Citizens Broadband Radio Service Device (CBSD) will first register with the SAS and provide its location information among other registration parameters, and then it will ask the SAS to grant access in a certain channel. Before granting access, the SAS will use information from the Environmental Sensing Capability (ESC) network to detect incumbent activity in the area where the CBSD operates. The SAS will also use measurement reports from the other CBSDs in the same area to determine the level of interference in a certain channel, as well as, if the channel needs to be protected due to PAL user activity.